Region: Enping 24-2 Oilfield, 200 km south of Hong Kong, China
Water Depth: 282 ft to 315 ft (86 m to 96 m)
Vessel: Maersk Attender AHTS, Bourbon Evolution 805 DSV, HYSY 289 installation vessel
Onshore and offshore project management, installation engineering and procedures development and installation of a new FPSO for China Offshore Oil Engineering Company (COOEC) – including full singlepoint mooring system, a fixed manned drilling and pipeline production platform, a 2.2 km subsea flexible pipeline and a subsea power/optical 2.2 km composite cable.
InterMoor was responsible for planning, engineering and installing 84" driven anchor piles with varying lengths (38 m-49 m), 12 chain/sheathed spiral strand wire mooring legs, STP buoy, 175 m dynamic riser with buoyancy modules, 1x12" production hose with 2450 m static flowline, re-routing and tie-in of pre-laid electric cables, 1 PLEM structure and 2 power cable support structures. As well, InterMoor was responsible for preparing procedures for DSV for riser tie-in.
Challenges faced during the project included:
- multiple vessels with simultaneous operations,
- 49 m long piles deployed from standard size ISV with 250t crane,
- uncertain vessel availability and restrictions on vessel winch bend radius needed for mooring wire installation.
To successfully complete this job, specific procedures and modifications were developed to allow the system to be installed as independently as required and without the need for divers.
InterMoor was able to accomplish this job by designing specific procedures to allow the deployment of 49 m piles from the barge by horizontally deploying them and then upending them on the seabed. The procedure also allowed the pile follower and hammer to be deployed separately, keeping the weights within crane capacity. As well, piles were installed separately by ISV, moorings were deployed independently with AHT to later be connected by DSV. Risers and power cables hung off independently to allow DSV tie-in when available. These procedures allowed the client to be flexible with vessel availability.
To solve the restrictive bend radius on the vessel winches for the mooring wire installation, InterMoor made structural modifications to the winch, adaptors and separators to increase diameter. To avoid the use of divers, an STP buoy hook-up was designed for use with MoorLok connectors. The STP buoy was lowered in the water column by two clump weights (for crane capacity) to ensure an easier connection and the ability for the system to be left partially installed in the event of a typhoon. InterMoor also created a wire “doghouse” to protect the mooring wires at the shark jaws during installation.
InterMoor placed an engineering team in China to work closely with COOEC during the onshore planning and engineering phase of this project, which lasted eleven months, commencing May 2013. The installation was completed within four months, from April to August 2014. InterMoor oversaw all project management and engineering, mobilized, prepared and outfitted all vessels required for installation, managed operation logistics and performed all marine operations within scope and on time.
Enping STP Buoy